Scientific opinion on the safety and efficacy of L-tyrosine for all animal species
2013
(FEEDAP), EFSA Panel on Additives and Products or Substances used in Animal Feed
L-Tyrosine can be synthesised in the body from L-phenylalanine, an essential amino acid. The additive L-tyrosine is produced by acid hydrolysis of feather keratin. L-Tyrosine is considered safe for all animal species, provided that the conditions of use are respected, i.e. supplementation of conventional diets with 0.5 % L-tyrosine for food-producing animals and 1.5 % for non-food-producing species. Higher dietary concentrations may lead to growth rate depression and eye lesions, and, in young animals, behavioural changes. L-Tyrosine will be incorporated into the body protein of the animal. The protein composition will not be changed. Free L-tyrosine will not be stored in the tissues. On the basis of the data available, no risk is expected for the consumer from the use of this L-tyrosine preparation showing a purity > 95 %. In the absence of data, the product is considered potentially irritating to skin and eyes, a potential dermal sensitiser and hazardous by inhalation. The use of L-tyrosine in animal nutrition would not be expected to lead to any localised increase in the concentration of L-tyrosine or its metabolites in the environment. It is concluded that the use of this product as a feed additive does not represent a risk to the environment. The supplementation of feed with L-tyrosine is efficacious in cases where high requirements for tyrosine as a melanin precursor occur. This has been demonstrated in cats for intensively colouring the coat. L-Tyrosine may also have the potential to intensify the pigmentation of the coat/plumage of other species, but limited evidence is available.
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